I. Field of the Invention
The present invention relates generally to railway car handling equipment and, more particularly, to a rail car spotting or indexing system which positions railroad cars along a specified section of track to be addressed during loading or unloading operations. Specifically, the invention deals with an improved cylinder-type, axle progressing system having dual coordinated progressors of variable-stroke and speed, wherein the position of each dog of each progressor is automatically controlled.
II. Discussion of the Related Art
Freight hauling railway cars are positioned near freight or cargo handling equipment during loading and unloading operations. Freight in the form of bulk cargo such as grain, coal, iron or the like is typically lifted or dumped into railway cars. Subsequently, the freight is emptied from the cars by gravity and received by stationary freight handling equipment such as chutes and conveyor equipment. Liquid bulk cargo is typically unloaded by opening drain valves connected to large hoses and associated pumping equipment. A railway car used for transporting coal, grain, or other finely divided dry bulk agriculture material is typically covered and has a plurality of spaced bottom discharge hopper bins or chutes accessing the main storage volume and closed by discharge gates. This type of rail car is designed to be positioned over dedicated recessed receiving facilities situated at fixed stations, such as grain or coal bins and conveyors positioned beneath the railroad track.
During the unloading operation of a coupled string of rail cars, a connected train engine roughly positions one end of the string of cars near the unloading area. Train engines are not well suited for indexing or precisely positioning individual cars or even sets of cars along the railroad track, let alone over individual car bins, chutes or conveyors. To this end, positioning devices known as railway car indexers or spotters have been built and operated at fixed stations.
Railway car indexers include at least one engaging member or "dog" for engaging at least one railway car in a string of cars and pushing or pulling the string a given distance along the railroad track. The engaging member is often situated and operated along an auxiliary indexer track or guideway juxtaposed in parallel relation to the railroad track in the fixed receiving facility. Fluid-operated actuators, such as chains and sprockets driven by hydraulic or electrical motors supply power are provided for moving the railway cars. The dogs of these devices typically operate against the lower or upper portion of the railroad car wheel truck frame (bogey frame). One such device is illustrated and described in co-pending application Ser. No. 08/580,810, filed Dec. 29, 1995, now U.S. Pat. No. 5,709,153, issued Jan. 20, 1998, and entitled "HIGH DOG INDEXER". That application is common of inventorship and assignee with the present application.
U.S. Pat. No. 4,006,691 issued to Kacir et al. and U.S. Pat. No. 4,354,792 issued to Cornish show train positioners including an engaging member arm which engages a car coupler from above. The engaging member arm is situated on a track or guideway next to the railroad track. Power is supplied to the positioner for moving the railway cars by a motor connected to a pulley and cable assembly. These positioners are quite large and complex, and initially aligning the railway cars with the engaging member arm such that the arm may be lowered to engage the car coupler may be difficult.
U.S. Pat. No. 3,696,754, issued to Anderson et al, describes a railroad car shifting system mounted between the tracks which employs axle engaging dogs pivotally attached to dog carriages or barneys which are situated in a guideway. Each dog is spring-biased to a raised position for engaging and pushing the next railroad wheel axle encountered as the barney is moved in one direction along the guideway by a hydraulic cylinder. Each dog in the '754 patent pivots to a lowered position when pushed or hit from behind (as on a return stroke), but must be manually depressed to allow a reversal of the direction of the string or trip of cars. The system includes a variable-stroke hand-off system having a pair of telescoping, single acting hydraulic actuators situated in a partially overlapping parallel arrangement. In the stowed position the piston of at least one of the actuators is exposed. The actuators are linked by a common cable and sheave arrangement in which the extension of one actuator in a power stroke pulls on the cable which, in turn, causes the collapse or retraction of the other. In operation, the dogs alternately engage the axles of the successive carriages in cars using a variable stroke operation. A long vane and lever arm are used to control the stroke of each actuator. Apparently, each actuator extends past a respective bogey axle and then the actuator reverses direction, forcing the dog into the axle. The distance that the actuator extends past the forward edge of the vane must be greater than the distance between the axles of each bogey. It is not apparent from the Anderson disclosure that the wheel axle smoothly transfers from one dog to the other.
A later patent (U.S. Pat. No. 4,252,064 to Ratcliffe, Jr.) discloses dogs that pivot to a lowered position when pushed or hit from behind (as on a return stroke), and may be lowered with an auxiliary hydraulic cylinder-operated mechanism when reversing the direction of travel of the cars.
U.S. Pat. No. 4,926,755, issued to Seiford, Sr., describes a reversing railway car moving system including a double truck assembly which operates in a guide track alongside the railroad track. Each truck of the double truck assembly includes two engaging members which are hinged together and spring biased to a raised position to form a peak at the hinge. In the raised position, the two trucks form a valley in which the bogey wheel truck frame is engaged on the lower portion for movement in either direction. A hydraulic cylinder in each truck is extended to lower the engaging members such that a railway car may freely pass over the double truck assembly. This reversing railway car moving system is powered by a cable and winch, and a double truck assembly may be positioned on one or both sides of the railroad track. Railway car indexers including a low dog which engages the lower portion of the truck frame work fine if the railway car is loaded to provide downward acting forces on the truck frame to prevent derailing. However, low dog engaging members may tend to lift the truck frame from the railroad track if the railway car is empty.
While these earlier arrangements have provided generally satisfactory operation, there remains the need to simplify the system by reducing the necessary moving parts and exposed mechanisms to improve operation and reduce the need for maintenance. The elimination of sheaves and cables or chains from the operation of such a system would clearly present an advantage. In addition, a simplification of the mechanical complexity associated with the operation of the dogs, together with better automation of the raising and lowering of the dogs is definitely desirable as is a reduction of the parts exposed to the environment when the system is not in use.